Mechanism of capillary electrophoresis enantioseparations using a combination of an achiral crown ether plus cyclodextrins.
The addition of an achiral crown ether (18-crown-6) to a cyclodextrin-based separation can significantly affect the capillary electrophoresis (CE) enantioresolution of organic racemates that contain a primary amine functional group. In most cases an enhancement of the enantioseparation was observed. However, there are also cases where the addition of 18-crown-6 was detrimental to a cyclodextrin-based CE enantioseparation. The effect of concentration of the two complexing additives as well as the effect of pH and added potassium ion were examined. A specific three-body complex involving simultaneous, dual inclusion complex formation can be used to explain both the enhanced and diminished enantioselectivities observed when 18-crown-6 is added to the run buffer.
Armstrong
D W
DW
University of Missouri-Rolla, Department of Chemistry 65401-0249, USA.
Chang
L W
LW
Chang
S S
SS
D000588:Amines / Q000737:chemistry*; D043844:Crown Ethers; D003505:Cyclodextrins / Q000737:chemistry* / Q000145:classification; D019075:Electrophoresis, Capillary / Q000379:methods*; D004986:Ether; D004988:Ethers, Cyclic / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009994:Osmolar Concentration; D010710:Phosphates / Q000737:chemistry; D011188:Potassium / Q000737:chemistry; D013237:Stereoisomerism
D000588:Amines; D043844:Crown Ethers; D003505:Cyclodextrins; D004988:Ethers, Cyclic; D010710:Phosphates; D004986:Ether; C015762:18-crown-6; D011188:Potassium